The present invention relates to a method and an apparatus for grinding the spherical surface of an optical lens or that of a mirror.
In recent years, optical technique has been utilized more and more in various industrial fields. Consequently, there is a growing demand for optical lenses and thus, the development of an apparatus for grinding a lens having high productivity.
The construction of a conventional apparatus of this kind is described below with reference to FIG. 9.
The apparatus comprises a grindstone rotating mechanism having a grindstone 50 for grinding and a grindstone rotating spindle 51 which rotates at a high speed of 20,000 rpm to 40,000 rpm with the grindstone 50 held at the lower end of the spindle 51; a feeding mechanism 57 for feeding the workpiece rotating mechanism toward the grindstone 50 along the rotary shaft of the spindle 51; a slide mechanism having a slide table 55 holding the grindstone rotating mechanism and the feeding mechanism and moving the grindstone rotating mechanism at a right angle to the direction in which the rotary shaft of the spindle 51 extends, thereby bringing the grindstone 50 into contact with a workpiece 56 at a predetermined position thereof and a servo-motor 58 for moving the slide table 55; a rotary base 52 holding the slide mechanism and being rotatable about a shaft 54 by a gear 53, for fixing the axial direction of the spindle 51 at a predetermined inclination; a collet chuck 59 for holding the workpiece 56 at an end of the shaft thereof confronting the grindstone 50; a motor for rotating the collet chuck 59; and an automatic loader 61 for supplying the workpiece 56 to the collet chuck 59 and removing therefrom.
The operation of the above-described apparatus is described below with reference to FIG. 9.
After the grindstone rotating mechanism is moved to a position at which the grindstone rotating mechanism does not interfere with the automatic loader 61, the ground workpiece 56 is removed from the collet chuck 59 by the automatic loader 61. Then, the unground workpiece 56 is supplied to the collet chuck 59. The inclination of the spindle 51 of the grindstone rotating mechanism is set to a predetermined angle by the rotary base 52 based on the spherical configuration of the workpiece 56. Then, the grindstone 50 is moved toward the workpiece 56 by the slide mechanism until the grindstone 50 reaches at a predetermined position. The workpiece 56 is rotated at a low speed by the motor 60 so as to feed the grindstone 50 rotating at a high speed toward the workpiece 56 by means of the feeding mechanism 57 driven by the servomotor 58 controlled by an NC apparatus. In this manner, the grinding of the workpiece 56 is completed with a predetermined rotation symmetry. Then, the grindstone rotating mechanism is moved away from the automatic loader 61 so that the grindstone rotating mechanism does not interfere with the automatic loader 61.
The construction of the above-described apparatus has the following disadvantage. That is, each time the grinding of the workpiece 56 terminates, the ground workpiece 56 is removed from the collet chuck 59 by the automatic loader 61 and the unground workpiece 56 is supplied thereto by the automatic loader 61. Accordingly, the grinding operation of the apparatus has to be stopped and in addition, the grindstone rotating mechanism must be moved upward by a great distance so that the grindstone rotating mechanism does not interfere with the automatic loader 61 while the workpieces 56 are being replaced with each other. Thus, it takes long for even a skilled operator to grind the workpiece 56 and thus the apparatus has a low productivity.